Question

我有一个奇怪的锁定问题，需要你的帮助来了解发生了什么。

使用查询，我在Prod_DW数据库中连接几个表（EventTransaction，Contact，Event和Outbound），并将结果保存到CustomDataExtract数据库的表中。

查询是这样的：

SELECT Col1, Col2, .... INTO CustomDataExtract..A1345_Contact_15022503
FROM Prod_DW..EventTransaction with (nolock) join ....

查询中使用的Prod_DW中的所有表都带有（nolock）选项，但在运行上述查询时，我仍然看到其他连接在Prod_DW表上被阻止。我的期望是，因为我查询使用with（nolock），在查询运行期间，它不应该对prod_DW表进行任何阻塞锁定。你能不能对此有所了解，并告诉我为什么我仍然看到其他连接被阻止。

以下是查询运行期间的Lock XML：

<Database name="CustomDataExtract">
  <Locks>
    <Lock request_mode="S" request_status="GRANT" request_count="1" />
  </Locks>
  <Objects>
    <Object name="(null)">
      <Locks>
        <Lock resource_type="DATABASE.BULKOP_BACKUP_DB" request_mode="NULL" request_status="GRANT" request_count="1" />
        <Lock resource_type="DATABASE.BULKOP_BACKUP_LOG" request_mode="NULL" request_status="GRANT" request_count="1" />
        <Lock resource_type="DATABASE.ENCRYPTION_SCAN" request_mode="S" request_status="GRANT" request_count="1" />
        <Lock resource_type="PAGE" page_type="*" request_mode="X" request_status="GRANT" request_count="1" />
      </Locks>
    </Object>
    <Object name="A1345_Contact_15022503" schema_name="dbo">
      <Locks>
        <Lock resource_type="ALLOCATION_UNIT.BULK_OPERATION_PAGE" request_mode="S" request_status="GRANT" request_count="1" />
        <Lock resource_type="HOBT.BULK_OPERATION" request_mode="IX" request_status="GRANT" request_count="1" />
        <Lock resource_type="METADATA.INDEXSTATS" request_mode="Sch-S" request_status="GRANT" request_count="1" />
        <Lock resource_type="OBJECT" request_mode="BU" request_status="GRANT" request_count="1" />
        <Lock resource_type="OBJECT" request_mode="X" request_status="GRANT" request_count="1" />
      </Locks>
    </Object>
  </Objects>
</Database>
<Database name="Prod_DW">
  <Locks>
    <Lock request_mode="S" request_status="GRANT" request_count="1" />
  </Locks>
  <Objects>
    <Object name="Contact" schema_name="dbo">
      <Locks>
        <Lock resource_type="OBJECT" request_mode="Sch-S" request_status="GRANT" request_count="9" />
      </Locks>
    </Object>
    <Object name="Event" schema_name="dbo">
      <Locks>
        <Lock resource_type="OBJECT" request_mode="Sch-S" request_status="GRANT" request_count="1" />
      </Locks>
    </Object>
    <Object name="EventTransaction" schema_name="dbo">
      <Locks>
        <Lock resource_type="OBJECT" request_mode="IS" request_status="GRANT" request_count="2" />
        <Lock resource_type="OBJECT" request_mode="Sch-S" request_status="GRANT" request_count="8" />
        <Lock resource_type="PAGE" page_type="*" index_name="ndx_EventTransaction" request_mode="S" request_status="GRANT" request_count="1" />
      </Locks>
    </Object>
    <Object name="Outbound" schema_name="dbo">
      <Locks>
        <Lock resource_type="OBJECT" request_mode="Sch-S" request_status="GRANT" request_count="1" />
      </Locks>
    </Object>
  </Objects>
</Database>

Answer 1

即使使用nolock，也始终会发生模式锁定。请阅读本文，了解有关nolock期间发生的事情的更多信息。

http://www.mssqltips.com/sqlservertip/2470/understanding-the-sql-server-nolock-hint/

SQL Server锁定问题

1 个答案: